First of all setup DNJL PPA to upgrade KVM/QEMU up to Qemu 0.12.5 & Libvirt 0.8.3 on Ubuntu Lucid Server and download the most recent Fedora virtio-win drivers from http://alt.fedoraproject.org/pub/alt/virtio-win/latest/images/bin as floppy and ISO image. Notice , that same virt-install will run fine on KVM Server Ubuntu 10.10 due to required versions of Libvirt & Qemu appear to be installed by default.